People respond differently to the same level of vitamin D supplementation, making it difficult to formulate one-size-fits-all guidelines.
Image thanks to plant nutrition.
Figuring our what level of vitamin D supplementation is necessary to bring one’s levels up to a specific blood level, like 30 ng/ml—the level associated with the longest lifespan, is not as easy as one might think. For example, here’s seven people starting out with blood levels under the target of 30. They all got the exact same same dose of vitamin D, 1600 IUs a day, and here's what happened to their levels over the next 6 months.
One person's blood levels tripled Another even quadrupled. But in these three, even though they were on the same dose, their blood levels hardly moved at all and stayed under 30.
So let’s say you’re trying to come up with a recommendation for people. Here’s a scatter plot of about 3000 people. Blood level versus intake. So people taking 10,000 a day average a blood level of about 75, with 95% of the people falling in between about 40 and 110. If we want to choose a dose for which 95% of people reach the target of 30, we’d probably choose something around 6000 a day, but though that would get the most to the minimum, ≈ the average level would be over 50, which is higher than we’d like to see on the U-shaped vitamin D total mortality graph. That's equivalent to like 125 nmol/L, which is off to the right of the graph. You can see why forming dietary recommendations is a formidable, and unenviable task.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by veganmontreal.
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Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. This is the sixth video in a nine day series on vitamin D. Be sure to check out yesterday's video-of-the-day Vitamin D supplements may be necessary.
For some context, please check out my associated blog posts: Vitamin D: Shedding Some Light on the New Recommendations, Eating To Extend Our Lifespan, and Vitamin D from Mushrooms, Sun, or Supplements?